Video shows smoke pouring from new SF Muni train near Montgomery station

Smoke poured from a new Muni train car approaching the Montgomery station in San Francisco before it was taken out of service Friday morning, according to the SFMTA. Muni tweeted that the train was reported to have a mechanical issue, and operators directed the train to bypass the station to be "aired out."

In video posted to Reddit, smoke fills the underground station creating a foggy haze as passengers tried to figure out what was going on.

Muni spokesperson Paul Rose told SFGATE, however, that the issue was likely "not specifically a mechanical issue," but "likely electrical in nature."

As Muni investigators found, the situation began when a mother was on a BART train at the Embarcadero station, while her child was on the platform.

"After learning the mother and child were separated, we called for the power to be shut off to stop all trains," Rose explained. "The child and mother were reconnected before the train left Embarcadero."

When the power started back up, it caused a surge. The train's pantograph, which Rose notes connects the train to electricity, began to smoke near the Montgomery Station. He believes it likely sparked.

The Montgomery station was then evacuated for 10 minutes as smoke cleared.

New MUNI trains sit on tracks at MUNI Metro East Maintenance Facility July 20, 2017 in San Francisco, Calif.

New MUNI trains sit on tracks at MUNI Metro East Maintenance Facility July 20, 2017 in San Francisco, Calif.

These new train cars, constructed in the Sacramento region by German manufacturer Siemens, were expected to "have a significant impact on Muni reliability," Muni spokesperson Paul Rose said a year ago.